There are line inkjet-type inkjet recording and image forming apparatuses which eject ink droplets from a recording head to perform recording, the devices including a line engine in which multiple recording heads (below simply called “heads”) are lined up in a main scanning direction. In such a line engine configuration, a configuration which makes it possible to replace one recording head is already known.
In the line engine in which the multiple heads are lined up, an ink supply flow path becomes long and also an amount of ink supplied becomes large. Therefore, a fluid resistance to a head from a sub tank provided in a body of the apparatus increases, so that a pressure loss becomes greater. The pressure loss leads to a shortage in ink supply, causing ejection failures (bending, non-ejection, entraining of air from a nozzle).
Nevertheless, when the ink supply flow path is thickened, a whole machine size becomes larger or air bubbles remain at the time of initial loading into the supply path. The remaining air bubbles block up the flow path, the flow path becomes thin, so that the fluid resistance increases, causing the pressure loss to become greater. Then, there is a problem that a shortage in ink supply occurs, causing ejection failures (bending, non-ejection, entraining of air from a nozzle).
JP2007-168421A (Patent Document 1) discloses that, with an aim to increase a speed of supplying liquid to a nozzle by decreasing a pressure loss and a liquid flow path resistance within a liquid ejection head, an ink supply chamber 44 is arranged to be laminated with a main ink supply chamber 42, and a filter 40 which intervenes between the main ink supply chamber 42 and the ink supply chamber 44 is arranged to extend along a face which is generally parallel to a nozzle arrangement plane on which multiple nozzles are lined up.
Moreover, JP2011-148224A (Patent Document 2) discloses that, with an aim to efficiently discharge air bubbles within a head tank, a filter member is provided in a head tank, the filter member dividing an upstream chamber and a downstream chamber, a supply path which provides ink from a downstream portion of an ink container to a head and a discharge path which discharges to the outside ink discharged from a discharge outlet portion of the head.
However, reduction in the pressure loss is not sufficient even with these related art techniques. Therefore, a problem of ejection failures occurring has not been solved. Moreover, an efficient discharging of air bubbles at the time of replacing one head or at the time of initial loading has not been achieved.